Lengthening a Charger Cord … to Save Our Car Trip

We are taking a LONG car trip. It would be great to use the power outlet in the back of the car to charge our hand-held game devices (a great pass time for the gamers in your group), but the cord is too short to reach the seats - what to do?

Step 1: Assemble Your Materials and Tools

Pull together all the materials and tools: the original charger cord, desired length of additional power cord of similar gauge containing at least two wires (we sacrificed an old mouse to get the cable; it happened to have four wires plus an uncovered ground-type wire), electrical tape, wire stripper tool (that can handle very small gauge wires), heat shrink tubing (the smallest size that will fit over the cable like a sheath) and a heat gun.

Step 2: Cut the Cables and Strip the Wires

Careful here! The wires are typically composed of fine strands of copper so it is easy to cut through them by accident. Strip the insulation (plastic cord cover), by about ¾”.

Pick the colour of the wires to be joined; match them if possible but identify and record your choices on paper so you know which ones to put together! We chose green to pink, and orange to black just because of the way the wires lined up naturally with each other.

Strip the four inner wires that will be joined by about ½”. The idea is to have enough bare wire to twist the pairs together, but also leaving some of the insulation on the individual wires to ensure that the bare strands do not touch between the wrong wires causing a short circuit. Twist the strands of the four individual wires to create a more solid wire for the next step.

Step 3: Position the Heat Shrink Tubing and Join the Wires

Cut two lengths of heat shrink tubing to extend on either side of the area of cable that will be joined (probably about 2” to 3”) and slide the two tubes onto on portion of the cable in preparation for the join. Now for the two joins! Twist the pairs of wire strands together ensuring that ONLY the intended strands of wire are touching each other (remember your colour choices to not get mixed up); be careful that there are no loose strands escaping your bundle. Use electrical tape to help hold each pair together as well as insulate the joined strands from each other. Carefully align the joins along the cable and then slide the pre-positioned heat shrink tubing to cover the two joined areas.

Step 4: Finish the Job and Test It Out!

Use the heat gun to shrink the tubing over the two joins; be careful with that heat gun as it only takes a bit of heat to do the job! Take your newly extended cable to the car, plug it in and activate the car’s electrical system … so great when it works: your gamers are good to go with charging their devices and hours of car ride entertainment (but they should not forget to look out the window once in a while)!

Troubleshooting: If it does not work, you can carefully strip off the tubing and electrical tape and start again - attention to detail is the secret to success … good luck!

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4 Discussions

Great idea and it's simple enough but be warned, the longer you make the cable, the longer it takes to charge. If it's a long cable and the insulation around it is thick, you'll experience voltage drop off which could potential harm a phone battery. Keep the charge cable under 10 feet and try to find an extension that has thicker insulation. As always, be careful with the positive and negative because they aren't always red and black

If you make an extension with only 2 wires and the data pins "programming" is in the charger end of the wire, your tablet will not know, that it's OK for it to draw 2A.

If your tablet is an Android, it needs its data pins shorted (tablet end) to signal that 2A can be drawn - If you do that, mark it as a charge only cable, as you won't be able to feed data through).

If your table is of the fruity persuasion, it needs different voltages on the data pins on the tablet end of a two wire extension (2.00V on D- and 2.75V on D+ for 2A and the opposite for 900mA). This takes 3 or 4 resistors, depending on method.

Just select a proper wire cross area and you can make it as long as needed (within reason of course). As an example... Using 10 feet of 16 AWG for the extension, and drawing 2A will result in a voltage drop of less than 200mV, well within the USB spec.

The thicker the insulation, the harder it will be for the copper to dissipate the power, so thick insulation is not really a dream scenario, if you want to keep the voltage drop down (to make it physically strong and resistant to shorts is an entirely different matter however...)

I'd really like to hear why you believe, that voltage drop in the charge cable could "potential harm a phone battery"?